Great amounts of effort have been expended in the prior art in connection with magnetic confinement of plasma for example in controlled thermonuclear fusion devices and the like. In this connection, the plasma comprises a highly ionized gas composed of a nearly equal number of positive and negative free charges (or positive ions and electrons). Because of the mutually coupled nature of electromagnetic fields within such a plasma and the motion of the plasma charges themselves, it has been well documented that the plasma can support unusual oscillations and wave motions, both stable and unstable. For example, stable and unstable wave motions in plasma are described by the McGraw-Hill Encyclopedia of Science & Technology, particularly in Volume 10, at pages 443-461 and Volume 14 at pages 501-507, both published by McGraw Hill Inc., 1977.
Further prior art work has been carried out in these areas having a closer relation to the method and apparatus of the present invention. A number of these prior art references are briefly described below.
1. Initially, work in connection with high-beta, hot-electron plasmas produced by electron-cyclotron heating was disclosed in an article by R.A. Dandl, H.O. Eason, P.H. Edmonds and A.C. England entitled "Resonance Effects on Electrons in Mirror-Contained Plasmas", Nuclear Fusion, 11 (1971). PA1 2. Efficient generation of hot-electron plasmas by microwave power with multiple frequency components was discussed in an article by B.H. Quon, R.A. Dandl, W. DiVergilio, G.E. Guest, L.L. Lao, N.H. Lazar, T.K. Samec and R.F. Wuerker entitled "Impact of Multiple-Frequency Heating on the Formation and Control of Diamagnetic Electron Rings in an Axisymmetric Mirror", Phys. Fluids, 28 (5), May 1985. PA1 3a. Work extending the results of a previous investigation of growing electromagnetic waves in a gyrotropic electron plasma to relativistic-electron energies was set forth in an article by R.N. Sudan entitled "Electromagnetic Instabilities in the Non-Thermal Relativistic Plasma", Phys. Fluids, 6, 57 (1963). PA1 3b. Related work concerning a governing equation for whistler modes in the Elmo Bumpy Torus is set forth in an article by P.N. Guzdar and R. Marchand entitled "Whistler Instability in the Elmo Bumpy Torus", Phys. Fluids. 25 (4), Apr. 1982. PA1 4. Production of a hot electron plasma in a magnetic-mirror field by high-power microwave discharges was disclosed in an article by H. Ikegami, H. Ikezi, M. Hosokawa, K. Takayama and F. Tanaka entitled "Microwave Burst at Triggered Instability in a Hot Electron Plasma", Phys. Fluids, 11 (5), May 1968. PA1 5. The effects of a relativistic electron population on the temporal and spatial growth rates of the whistler instability were described in an article by N.T. Gladd entitled "The Whistler Instability at Relativistic Energies", Phys. Fluids, 26 (4), Apr. 1983. PA1 6. Further work in the area of unstable electromagnetic waves similar to whistler modes was disclosed in an article entitled "Electromagnetic Ion Cyclotron Instability Driven By Ion Energy Anisotropy In High-Beta Plasmas", Phys. Fluids, 18, 1045 (1975). PA1 7. Additional work concerning the ability of magnetically confined plasmas created and heated by electromagnetic fields near the electron gyrofrequency to support wave instability was disclosed in an article by G.E. Guest and D.J. Sigmar entitled "Stability of Microwave-Heated Plasmas", Nuclear Fusion, 11 (1971). PA1 8. The theoretical rates of amplification of whistler waves propagating through hot-electron plasmas with anisotropic pressures was discussed in an article entitled "Amplification of Whistler waves Propagating Through Inhomogeneous Anisotropic Mirror Confined Hot-Electron Plasmas" by G.E. Guest and R.L. Miller in Phys. Fluids, 3690 (1988). PA1 9. Both experimental and theoretical studies of hot-electron plasma generation using oppositely directed co-linear steady-state streams of energetic electrons interacting with a background plasma have been reported in numerous articles many of Which are cited in an article entitled "Oscillations Present in Plasma Electron Heating by an Electron Beam" by I. Alexess, G.E. Guest, D. Montgomery, R.V. Neidigh, and D.J. Rose in Phys. Rev. Letters, 344 (1968). PA1 10. A theoretical analysis of the three-wave processes by which oppositely directed co-linear steady-state streams of energetic electrons interacting with a cold background plasma can produce electromagnetic waves suitable for generating hot-electron plasmas is presented for example in a book entitled Plasma Astrophysics by S.A. Kaplan and V.N. Tsytovich, published by Pergamon Press (Oxford) 1973. PA1 11. Recent experiments and theories of the three-wave processes by which oppositely directed colinear steady-state streams of energetic electrons interacting with a cold background plasma can produce electromagnetic waves at twice the upper hybrid frequency was reviewed in an article entitled "Experimental Observations of Non-Linearly Enhanced 2.OMEGA..sub.uh Electromagnetic Radiation Excited by Steady-State Colliding Electron Beams" by T. Intrator, N. Hershkowitz and C. Chan. in Phys. Fluids, 527 (1984).
Rather than repeating substantial background information provided for example by the above references, each of the above references is incorporated herein as though set out in its entirety.
Generally, prior art references such as those noted above have dealt with the use of conventional sources of microwave energy to create and sustain magnetically confined plasmas for a variety of applications, together With an identification of the instabilities that can occur in such plasmas. However, there has generally been found to remain a need for a method and apparatus for generating microwave energy at high power levels substantially greater than those contemplated in the prior art while adapting the form of the high-power microwave energy for a number of different application.
U.S. Pat. No. 4,733,133 issued Mar. 22, 1988 to the inventor of this invention disclosed another method and apparatus for producing microwave radiation. The method and apparatus of that invention included certain features in common with the present invention, particularly in connection with extraction of a beam of microwave pulses from the chamber and direction toward a suitable target. Accordingly, that patent is incorporated herein by reference in order to provide a more complete understanding of the present invention.